Only ADHD persons who are regularly prescribed a classic psychostimulant(Ritalin, dexedrine, etc) will be recruited. This will confirm that such persons show a beneficial therapeutic response to stimulants that can be characterized using brain function measurements. While this will prevent the comparison of brain activity response among various medications, it will simplify interpretation of the results. Finally, subjects will be excluded if they are taking any adjunctive medication for ADHD symptoms (e.g., Wellbutrin, etc.) or another psychoactive medication.